Infants' formation of lexical categories: Effects of variability and
constancy

Leher Singh
Sargent College
Boston University

Individual instances of a word are encountered in varying forms, depending
on context or indexical cues. To recognize words, infants must identify
acoustically distinct tokens as phonetically and lexically equivalent. The
use of acoustic cues to meaning differs across languages, so infants
cannot know a priori which cues are lexically relevant. This is reflected
by the fact that young infants, at 7.5-months, are highly sensitive to the
physical form of an instance, rendering their word recognition capacities
fragile. By contrast, at 10.5 months, infants are able to recognize
dissimilar tokens of a word. Previous research shows that the degree of
variability across encounters of a word strongly affects infants' early
formation of lexical categories. Experience with highly variable tokens of
a word facilitates mature word recognition based on lexical identity, even
for low variability tokens that are presented conjointly. Conversely,
experience with low variability tokens of a word limits infants' abilities
to form lexical categories by directing their attention to
exemplar-specific properties. This suggests that the degree of variability
in the input either facilitates or impedes word recognition by emphasizing
defining characteristics of lexical types or tokens respectively.